Standard trademark defense suit filed by a corporation - defend it or lose it. The judge will either say it’s infringing, and they have to stop, or it’s unrelated to the Batman character, so Warner gets a paper trail. A trail saying that they’re continuing to defend their mark so that future entities wanting to make T-shirts with logos that look awfully close to Batman’s logo won’t be able to claim that the mark was abandoned.

Trademark law is weird and stupid, but this doesn’t look frivolous. It just looks like how a law written to protect corporate identities works when those corporate identities become things that you sell to people to wear on a T-shirt.

Indeed, however I would call it frivolous because infringement occurs when the trademark is confusingly similar to a trademark owned by another party, in relation to products or services which are identical or similar to the products or services which the registration covers.

Called “Likelihood of confusion”
from: http://www.law.cornell.edu/wex/trademark_infringement
When the alleged infringer and the trademark owner deal in competing goods or services, the court rarely needs to look beyond the mark itself; infringement will usually be found if the two marks at issue are sufficiently similar that consumer confusion can be expected. If the goods in question are completely unrelated, confusion is unlikely and infringement will generally not be found.

That’s pretty much got all the options covered for drawing a stylized bat. Doesn’t matter too much how you stylize it, it’ll look like some incarnation of a Batman logo.

It doesn’t seem reasonable to me that you wouldn’t be able to use any kind of sylized bat whatever for a logo, particularly a logo of a thing that’s clearly not a comic book / movie hero. I mean, are they going to argue that people might confuse a Valencia FC football match with a Batman fans convention? That sounds like a hard sell in court…

You’ve got more experience in the area than I do, as a graphic designer. The question I have is with increasingly symplified geometric designs, aren’t we headed for a lot of collisions in the Trademark space?